Stabilised polyamides containing a copper salt and a phosphine



United States Patent US. Cl. 26045.75 4 Claims ABSTRACT OF THEDISCLOSURE A thermally stabilised polyamide comprising a high' molecularweight polyamide and as a stabilising agent a combination of copper saltand a phosphine and optionally an inorganic or organic salt of hydriodicacid.

This invention relates to stabilised polyamides using copper compoundsas stabilisers.

Mouldings of polyamdes obtained by polymerising diamines withdicarboxylic acids or from aminocarboxylic acids or their lactarns; forexample filaments, bristles or films, are deteriorated by the action ofair and oxygen, particularly at elevated temperatures, to such an extentthat their relative viscosity decreases whilst their strength andelasticity deteriorate. At the same time, the polyamide becomesprogressively browner in colour.

It is known that polyamides can be protected against deterioration bythe action of air and oxygen at elevated temperatures by the addition ofstabilisers. The following compounds, for example, have already beenused as stabilisers: manganese salts of inorganic or organic acids;copper salts of inorganic or organic acids; derivatives of the oxyacidsof phosphorus; aromatic amines and phenols. Combinations of these groupsof compounds with one another or with compounds Whch, on their own, haveno stabilising action, such as alkali metal halides, alkaline earthmetal halides, iodine and arylsulphonic acids, have also been used toadvantage.

The known stabilisers, however, have the disadvantage either that theirstabilising action is too weak, as is the case, for example, withmanganese salts, phosphorus compounds and phenols, or the disadvantagethat they cause discolouration, particularly when they are added to thepolyamide-forming starting mixture before polymerisation, as is the casefor example with copper salts, or that they are sensitive to light and,over a period of time, discolour the polyamide, as is the case forexample with aromatic amines and phenols.

It has now been found that polyamides can be stabilised without theaforementioned disadvantages by using, as the stabiliser, a combinationof (a) a salt of monovalent or bivalent copper with an inorganic ororganic acid, and (b) aphosphine.

A further object of this invention is to combine the stabilising mixtureconsisting of a copper salt and a phosphine with an inorganic or organicsalt of hydriodic acid.

The more difficulty volatile compounds from the triaryl-, trialkylortri-(aryl-alkyD-phosphine series are preferably used in accordance withthe invention as the phosphines. Examples of such phosphine aretriphenyl phosphine, tris-(dimethylaminophenyl)-phosphine, tritolylphosphine, phenyldimethyl phosphine, dimethylarninophenyl-dimethylphosphine, naphthyl diethyl phosphine, tributyl phosphine, tripentylphosphine, trioctyl phosphine,

3,505,285 Patented Apr. 7, 1970 ICC tris-(hydroxy-ethyl)-phosphine andtricyclopentyl-phosphine.

Preferred copper salts are the cupric and cuprous salts of hydrohalicacids and hydrocyanic acid, and the copper salts of aliphatic carboxylicacids.

Examples of suitable copper salts are cuprous chloride, cuprous bromide,cuprous iodide, cuprous cyanide, cupric chloride, cupric acetate andcupric stearate.

The copper salts are preferably added in such a quantity that thepolyamide contains 0.0001 to 0.1% by weight, most preferably 0.001 to0.02% by weight, of copper. The phosphorus compounds are preferablyadded in such a quantity that the polyamide contains 0.001 to 0.1% byweight, most preferably 0.001 to 0.05% by weight, of phosphorus.

Example of suitable inorganic or organic salts of hydriodic acids are:

(1) Ammonium iodide, sodium iodide, potassium iodide, calcium iodide,magnesium iodide, zinc iodide or cadmium iodide.

(2) Hydriodides of primary amines, such as hexadecylamine hydriodide;hexamethylene diamine dihydriodide and cyclohexylamine hydriodide.

(3) Hydriodides of secondary amines, such as N-ethylbenzylaminehydriodide; piperidine hydriodide and N- methyloctadecylaminehydriodide.

(4) Hydriodides of tertiary amines, such as N,N- dimethylbenzene-aminehydriodide; N,N,N-triethanolaminehydriodide; pyridine hydriodide;trioctadecylaminehydriodide and N,N-dimethyldodecylamine hydriodide.

(5) Iodides of quaternary ammonium compounds, such asN-benzyl-N,N,N-trimethylammonium iodide; N-ethyl-N-benzyl-N,N-diethylammonium iodide; N-dodecyl-N,N, N-triethyl-ammoniumiodide and N,N,N,N',N,N-hexamethyl-N,N-ethylene-bis-ammonium iodide.

(6) Hydriodides of aminocarboxylic acid esters and amides, such asN,N-dimethyl-6-aminocaproic acidmorpholide hydriodide; N,N dimethyl 6aminocaproic acid dodecylamide hydriodide; N-methyl-N-cyclohexyl-6-aminocaproic acid ethyl ester hydriodide andN,N-dimethyl-1l-aminoundec-anic acid anilaide hydriodide.

(7) Iodides of carbamylamrnonium compounds, such as N-(N-dodecylcarbamylpentyl) N,N,N trimethylammonium iodide andN-(N'-3,4-dichlorophenylcarbamylpentyl) -N,N,N-trimethylammonium iodide.

The inorganic or organic salts of hydriodic acid are preferably added insuch quantity that the polyamide contains 0.001 to 5% by weight, mostpreferably 0.01 to 1.0% by weight, of iodine.

The combinations according to the invention of copper salts andphosphorus compounds can be either mixtures of the components, orstable, crystallised addition compounds of phosphines and substancescorrespond ing to the formula CuX, in which X represents chlorine,bromine, iodine or cyanogen. Example of these addition compounds whichcan be obtained from the components, optionally at elevated temperature,are CuC1 2 triphenyl phosphine, CuBr 2 triphenyl phosphine, CuItri-nbutylphosphine, CuI .tri-n-pentylphosphine, Cul X 2 triphenylphosphine and CuCNXtriphenyl phosphine.

The stabiliser combinations according to the invention may be added tothe polyamide-forming starting mixture before polymerisation, afterwhich polymerisation may be carried out either continuously or inbatches, as known per se, Without there being any discolouration of thepolyamide melt.

It is also possible, however, to mix the stabilisers according to theinvention with the polyamide melt, either during or afterpolymerisation, in which case known mixing units, such as extruders orkneaders, may be used.

In addition to the stabilisers according to the invention, thepolyamides may also contain the usual additives such as pigments, dyes,light stabilisers, fillers such as glass fibres, lubricants,mould-release agents and crystallisation activators.

The polyamides stabilised in accordance with the invention against, inparticular, damage by oxidation at elevated temperatures, are eminentlysuitable for the production of industrial silk for fishing nets, drivebelts, conveyor belts, tyre cord and mouldings exposed to thermalstressing in the presence of air or oxygen.

Broadly speaking, the advantages set out below can be obtained by usingcopper compounds in combination with phosphines, optionally togetherwith inorganic or organic salts of hydriodic acid. These advantages canbe explained by the chemical resistance of the phosphines to hydrolysingor decomposing agents, and by the fact that secondary reactionsinvolving the products of hydrolysis or decomposition are avoided.

No discoloured products are formed in cases where addition precedespolymerisation and where screw extruders are used for mixing. The use ofscrew extruders is not accompanied by the formation of partlycrosslinked products (as is the case, for example, when aliphatic oraromatic esters of phosphoric or phosphorous acid are used, cf.comparison Example 4), or by corrosion (as in the case, for example,when halides of phosphoric or phosphorous acids are used). In addition,there is no additional chain-terminating effect where addition precedespolymerisation (as is the case, for example, with phosphoric orphosphorous acids or hydrolysable derivatives thereof).

The following examples illustrate more specifically the invention.

EXAMPLE 1 A mixture of 1.1 kg. of caprolactam, 35 g. of aminocaproicacid and 0.79 g. of CuCI 2 triphenyl phosphine (corresponding to 0.008%by weight of copper and 0.008% by weight of phosphorus in the endproduct), is polycondensed in the usual way in an auto clave at atemperature of 270 C. The resulting polyamide is then spun into afilament, chapped into granular form, freed from monomeric components byboiling with water and then dried. The resulting product is completelycolourless and has a relative viscosity of 3.12 (measured on a 1% byWeight solution in m-cresol). In order to test the stability of theproduct to atmospheric oxidation, it is stored at 150 C. in a dryingcabinet to which air has free access. After 144 hours, its relativeviscosity is 3.46, after 500 hours it is 3.16 and after 1000 hours it is2.96.

In the case of a comparison product of identical rela tive viscosity inwhich no stabiliser was present, the relative viscosity dropped underthe same conditions to 2.61 after 144 hours, to 2.36 after 500 hours andto 2.21 after 1000 hours. In addition, the comparison product becamemuch darker brown in colour considerably more quickly.

EXAMPLE 2 As in Example 1, a polyamide with a relative viscosity of 3.18is prepared from 0.30 g. of Cu(II)Cl 2I-l O (corresponding to 0.011% byweight of copper in the end product) and 0.52 g. of tripheuyl phosphine(corresponding to 0.006% by weight of phosphorus in the end product).The product is completely colourless. After it has been stored at 150 C.in a drying cabinet to which air has free access, its relative viscosityis 3.48 after 144 hours, 3.09 after 500 hours and 2.94 after 1000 hours.A polyamide prepared under identical conditions, except that only 0.30g. of Cu(II)Cl 2H O are added, is greenish in colour.

EXAMPLE 3 2 kg. of polycaprolactam with a relative viscosity of 3.15 arefused by means of a conventional screw extruder EXAMPLE 4 As in Example3, a polyamide with a relative viscosity of 3.01 is prepared from 0.35g. of Cu(II)-acetate H O (corresponding to 0.006% by weight of copper)and 0.44 g. of diphenyl ethyl phosphine (corresponding to 0.003%phosphorus). The product is completely colourless. After it has beenstored at C in a drying cabinet to which air has free access, itsrelative viscosity is 3.24 after 144 hours, 3.05 after 500 hours and2.92 after 1000 hours. A polyamide prepared under identical conditions,except that only 0.35 g. to Cu(-II)-acetate were added, is slightlygreyish-green in colour.

Comparison tests demonstrating the technical advance of the combinationof copper compounds with phosphines over combinations with otherphosphines, are set out in the following:

(a) A mixture of 1.1 kg. of caprolactam, 35 g. of aminocaproic acid and0.91 g. of Cu(I)-Cl 2 tripheuyl phosphite (corresponding to 0.008% byweight of copper and 0.009% by weight of phosphorus in the end product)is polycondensed in the usual way in an autoclave at a temperature of270 C. The resulting polyamide is then spun into a filament, choppedinto granular form, freed from monomeric components by boiling withwater and then dried. The resulting product is deep blue-grey in colour.

(b) As in comparison example (a), a deep blue-grey coloured polyamide isobtained from 0.50 g. of Cu(I)-I- triisopropyl phosphite (correspondingto 0.008% by weight of copper and 0.004% by weight of phosphorus in theend product).

(c) As in comparison example (a), a deep-blue-grey coloured polyamide isobtained from 0.32 g. of Ou(II)- Cl .2H O (corresponding to 0.012% byweight of copper in the end product) and 1.24 g. of trinonylphenyl phosphite (corresponding to 0.006% by weight of phosphorus in the endproduct).

((1) 2 kg. of colourless polycaprolactam with a relative viscosity of3.15 are fused by means of a conventional screw extruder in which theyare homogeneously mixed with 1.44 g. of Cu(I)Cl-triphenyl phosphite(corresponding to 0.011% by weight of copper and 0.0055% by weight ofphosphorus). The product is then spun into a filament, chopped intogranular form and dried. It is reddish-brown in colour and has arelative viscosity of 3.38.

Triphenyl phosphine on its own does not have any stabilising effect onpolyamides. This is demonstrated by the following comparison test:

2 kg. of polycaprolactam with a relative viscosity of 3.11 are fused bymeans of a conventional screw extruder in which they are mixed with 10g. of triphenyl phosphine (corresponding to 0.059% by weight ofphosphorus). The polyamide is then spun into a filament, chopped intogranular form and dried. It is colourless and has a relative viscosityof 3.02. After it has been stored at 150 C. in a drying cabinet to whichair has free access, its relative viscosity drops to 2.65 after 144hours, to 2.48 after 500 hours and to 2.24 after 1000 hours.

EXAMPLE 5 1 kg. of a conventionally prepared colourless polycaprolactamwith a relative viscosity of 3.12 (measured on a 1% by weight solutionin m-cresol), is fused by means of a conventional screw extruder inwhich it is homogeneously mixed "with various stabilisers. Thestabilised polycaprolactam is spun itno a filament of approx. 3 mm.diameter, chopped into granular form and dried. The granulate is thenstored at 150 C. in a drying cabinet to which air has free access, andits relative viscosity measured after 144, 500 and 1000 hours.

ondary amine, a hydroiodide of a tertiary amine, an iodide of aquaternary ammonium compound, a hydroiodide of an amino carboxylic acidester, 21 hydroiodide of an amino carboxylic acid amide, and an iodideof a carbamyl ammonium compound, said copper salt being present in such5 The test results are Set out In Table a quantity that the polyamidecontains 0.0001 to 0.1% by EXAMPLE 6 Weight of copper, said phosphmebeing present in such A mixture of 1.0 kg. of caprolactam, 35 g. ofamino- 3 l g tlfiat i g il z to 9 caprorc acid and the stabllisers setout 1n Table II, 18 poly- Welg t P osp orus sa t o y acld belngcondensed in the usual Way in an autoclave at a tempera 10 present insuch a quantity that the polyamlde contalns ture of 270 C. The colour ofthe resulting polyamides 1s O-OOI t y Welght of lodlneshown in Table II.3. The thermally stabilised polyamide of claim 2,

TABLE I Relative viscosity Percent Percent Percent Colour after- I inthe Cu in P in the of the polythe polypolypoly- After 144 500 1,000 No.Iodide g amide Cu-eompound amide amide amide mixing hours hours hours 0.38 011(1) Cl-1 triphenyl 0. 64 0. 011 0. 0055 Colour- 2. 98 4. 09 3. 843. 60

phosphine. less. 0.17 Cu(I)-I-2 triphenyl 1.26 0.011 0. 011 do.. 3. 124.17 3.89 3.66

phosphine. 0. do 1. 26 0. 011 0. 011 do 3. 08 3. 71 3. 55 3. 0.76Cu(I)CN- triphenyl 1.20 0.11 0.011 do 3.03 4.40 4.21 3.75

phosphine. 0.38 C11(I)Br-1 triphenyl 0.54 0.0085 0.004 d0 3.06 4.04 3.703.35

phosphine. 6 N,N-dimethyl-dodecylamine l. 0. 056 Cu(I)-I-2 triphenyl 1.26 0. 011 0. 011 do 3. 10 3. 92 3. 56 3. 20

hydroiodide. phosphine. 7 N,N-dimethyl-benzylamine 1. 16 0. 056 do 1. 260. 011 0. 011 do 3. 05 3. 86 3. 3. 16

hydro-iodide. 8 N-dodecyl-N,N,N-trimethyl- 0. 63 0. 022 do 1. 26 0. 0110. 011 do. 3. 05 3. 64 3. 25 2. 97

ammonium iodide. 9 "do 1. 57 0. 056 .do 1. 26 0. 011 0. 011 do 3. 05 3.81 3. 48 3. 12 10 N-ethyl-N-benzyl-N,N- 1.28 0.056 .....(10 1.26 0.0110.011 do 3.06 3.82 3.55 3,38

dimethylammom'nm iodide. 11 N,N-dimethyl-6-amino- 2. 01 0. 056 do 1. 260. 011 0. 011 do. 3. 05 3. 86 3. 72 3. 25

caproic acid dodecyl amide hydro-iodide. 12 N-(N-3,4diehlorophenyl 0. 790 022 dO 1 26 0. 011 0. 011 do. 3. 08 3. 65 3. 29 3. 06

carbamyl-pentyl)N,N,N- trimethyl-ammonium 13 d0 1. 26 0.011 0.011 do3.12 3.43 3.12 2.00 14 -410-.- 3. O0 2. 73 2. 36 2. 21

TABLE II Percent I Percent Cu Percent P Colour Test in the in t e in theof the No. Iodide G. polyamlde 011-compound G. polyamide polyamidepolyamide 1 KI 5.0 07 38 Cu(I)C1-1tripheny1phosphine. 0.64 0. 011 0.0055colourless. 2 KI 2. 0 0.17 Cu(I)I-2 triphenyl phosphine 1.26 0.011 0.011Do. 3 KI..- 1.0 0.10 do 1.26 0. 011 0. 011 Do. 10.0 0.76 Cu(I)CN-2triphenylphosp 1.10 0.011 0.011 Do. KI 5. 0 0.38 Cu(I)Br-1 triphenylphosphine. 0. 54 0.0085 0.004 Do. ,N-dimethyLdodecylamine- 1. 50 0. 056Cu(I)I-2 triphenyl phosphine 1. 26 0. 011 0. 011 D0.

hydroiodide. 7 N-dodecyl-N,N,N-trimethy1 1.57 0.056 d0 1.26 0.011 0011Do,

ammonium hydroiodide. g N,N41imethyl-fi-amino-caproie 2.01 0.056 .d01.26 0.011 0,011 Do.

acid dodecylaminehydroiodide. 9 KI 5.0 0.38 Cu( I) 01521120 triphenyl 0.27 0.011 0,0 5 Do,

phosphine. 0. 42 10 KI 5.0 0- 8 C11( z-2Hz0 0.27 0.011 Greenish.

What we claim is:

1. A thermally stabilised polyamide comprising a high molecular weightpolyamide and as stabilising agents admixed therewith (a) a copper saltselected from the group consisting of a chloride, bromide, iodide,cyanide, and a salt of an aliphatic carboxylic acid of monovalent andbivalent copper, and (b) a tertiary phosphine, said copper salt beingpresent in such a quantity that the polyamide contains 0.0001 to 0.1% byweight of copper, said phosphine being present in such a quantity thatthe polyamide contains 0.001 to 0.1% by weight of phosphorus.

2. A thermally stabilised polyamide comprising a high molecular weightpolyamide and as stabilising agents admixed therewith (a) a copper saltselected from the group consisting of a chloride, bromide, iodide,cyanide, and a salt of an aliphatic carboxylic acid of monovalent andbivalent copper, (b) a phosphine, and (c) a salt of hydroiodic acidselected from the group consisting of ammonium iodide, sodium iodide,potassium iodide, calcium iodide, magnesium iodide, zinc iodide, cadmiumiodide, 21 hydroiodide of a primary amine, a hydroiodide of a sec- 5wherein said salt of hydriodic acid is potassium iodide.

4. The thermally stabilised polyamide of claim 2, wherin said salt ofhydriodic acid is N,N-dimethyldodecy1- amine hydroiodide.

References Cited UNITED STATES PATENTS DONALD E. CZAJA, Primary ExaminerV. P. HOKE, Assistant Examiner US. Cl. X.R.

